Decoupling capacitors on semiconductor devices are essential components used to filter much of the noise that may be present between operating supplies such as power and ground. Some fabrication processes construct decoupling capacitors on a silicon substrate by forming one electrode into the substrate itself and then forming a second electrode out of an overlying conductive material with the two electrodes being separated by a dielectric material.
The formation of the decoupling capacitors in such a fashion leaves the substrate and capacitor dielectric susceptible to subsequent process steps, such as, future dopant implants that can penetrate into the silicon substrate and thereby causing "popping" where the two electrodes short together through the capacitor dielectric. Also, subsequent plasma etches can cause further damage reducing the overall surface area of the second electrode if it is not protected. Studies have shown that there is a correlation to capacitor damage to the spacer (plasma) etcher and etch time.
What is needed is an improved decoupling capacitor fabrication process whereby the capacitance is not further reduced but instead further increased.